Bizarre 320kbps files?

[Andreas Lilja]

Hi,

 

So basically I've been using Spectro (spectrogram program) on my music collection, and I've stumbled on a few oddities. A few of my Iron Maiden albums (all in .mp3 format) have some cutoffs like 16Hz or 18Hz despite being ripped directly from the retail-bought legit CDs at 320kbps CBR (in Windows Media Player). I tried re-ripping a few tracks to compare and they have the same frequency than my old archived ones. Is the record label master at fault? 

 

[vanished]

They may have just removed those frequencies in the studio.  Remember that CDs are generally at 44.1 kHz, so once you get up to like 22 kHz "sine wave", it's actually just a triangle wave  so they may have removed it since it wouldn't have sounded good and few people can hear above 18 kHz anyway (like basically no one after about 20 years old).

 

To check you could try ripping the CD to 192 kHz FLAC/WAV.  If it also shows up like this then, you know it's the CD and not the MP3 process.

 

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hold on I think I just misread that  sorry

 

If you are seeing cut offs at the low end (16 - 18 Hz, not kHz), well, basically my same exact logic stands; try ripping to WAV and compare, but odds are it's just not there since people can't really hear below 20 Hz.

[Andreas Lilja]

Just tried what you suggested, there's a 20-ish cutoff with WAV or WMA lossless. Seems like a MP3 encoding problem (?) of Windows Media Player, even if 320kbps CBR is ticked. Can't really say I notice it.

[vanished]

1 minute ago, Raskolnikov said:

Just tried what you suggested, there's a 20-ish cutoff with WAV or WMA lossless. Seems like a MP3 encoding problem (?) of Windows Media Player, even if 320kbps CBR is ticked.

It could be a technical limitation of the format, or it could be a setting in your encoder, or even a matter of "that's just how mp3 does it".  You could rule out all of those as far as I can tell by checking other mp3's you've made so far.

[Pomfinator]

Sounds like WMP is applying a low-pass filter on it's MP3 encode without telling you about it.

 

Try using Foobar to convert instead.  Set it up with LAME MP3 and see if 320kbps files still cut off at 18k.

[Guest]

That sounds normal, although I'd need to see the file to be sure.

 

For one, most music doesn't contain frequency content that low. For another, I believe that all levels of mp3 have low pass filtering - and some music may just be mastered that way to filter out noise.

[Andreas Lilja]

Thanks all for your replies.

14 hours ago, Ryan_Vickers said:

You could rule out all of those as far as I can tell by checking other mp3's you've made so far.

WMP rips most other albums correctly at 20.5Khz as it should. It's been on the same setting for years, I haven't changed anything; and there isn't much to do option-wise.

 

8 hours ago, Pomfinator said:

Sounds like WMP is applying a low-pass filter on it's MP3 encode without telling you about it.

 

Try using Foobar to convert instead.  Set it up with LAME MP3 and see if 320kbps files still cut off at 18k.

Tried with iTunes and got 19Khz instead of 16.5Khz. 

 

However can't really say I'm noticing a difference, even with Sennheiser HD 650s. It seems the file is really 320kbps, even if the spectrogram is showing it to be a crappy 128kbps one. 

 

 

 

[vanished]

2 hours ago, Raskolnikov said:

Thanks all for your replies.

WMP rips most other albums correctly at 20.5Khz as it should. It's been on the same setting for years, I haven't changed anything; and there isn't much to do option-wise.

 

Tried with iTunes and got 19Khz instead of 16.5Khz. 

 

However can't really say I'm noticing a difference, even with Sennheiser HD 650s. It seems the file is really 320kbps, even if the spectrogram is showing it to be a crappy 128kbps one. 

I don't believe it's possible to tell the bitrate of a file solely by the spectral frequency chart.

[Andreas Lilja]

Really? I thought the following was authoritative: https://www.whatinterviewprep.com/prepare-for-the-interview/spectral-analysis/

 

Took a few screenshots.

Comparison between iTunes and WMP: 

 

Comparisong between MP3 and WAV (lossless)

 
 
Really weird that WMP is sometimes ripping to 128kbps-ish frequencies when 320kbps is clearly chosen. 

[Andreas Lilja]

On 6/8/2016 at 3:44 PM, Ryan_Vickers said:

I don't believe it's possible to tell the bitrate of a file solely by the spectral frequency chart.

I think you're actually onto something!

 

Here's a live song from King Crimson, 320kbps. Ripped from WMP 12.

 

The green data seems like the only thing that matters. 

 

Here's the same file ripped as a 320kbps from Exact Audio Copy.